Biochemistry

Question 1

Name the two carbohydrate chains that make up starch

Answer 1

Amylose and Amylopectin

Question 2

Why can cellulose not be browk down by humans?

Answer 2

They dont have the enzyme cellulase to break it down

Question 3

Give 2 functions of chitin

Answer 3

• Cells walls of fungi

- Outer skeletons of insects

Question 4

Where is N-linked glycosylation added and modified?

Answer 4

Added in the endoplasmic reticulum and modified in the golgi complex

Question 5

What is Aggrecan an example of?

Answer 5

A proteoglycan with extensive O-linked glycosylation on the core protein (link protein). Forms a bottlebrush shape.

Question 6

What is the main enzyme involved in glycogen breakdown?

Answer 6

Glycogen phosphorylase

Question 7

Why is an enlarged liver caused by a type 1 glycogen storage disease?

Answer 7

Excessive glycogen storage

Question 8

Which hormone is released in response to an increase in blood glucose levels?

Answer 8

Insulin

Question 9

Compare the 3 types of diabetes

Answer 9

Type 1 = very low insulin and no response to glucose loading
Type 2 = normal/high insulin and no response to glucose loading
Type 3 = normal insulin, delayed response to glucose loading

Question 10

What is the result of hyperinsulinism?

Answer 10

Persistent hypoglycaemia

Question 11

Which condition in sheep is characterised by hypoglycaemia?

Answer 11

Pregnancy toxaemia

Question 12

Glycogen is primary stored in and used by which type of muscle fibres?

Answer 12

white glycolytic skeletal muscle fibres = fast fibres

Question 13

How many enzymatic reactions are needed to convert glucose to pyruvate?

Answer 13

10

Question 14

What types of tube are used for glucose collection and why?

Answer 14

Fluoride

- stop red blood cells from metabolising glucose other levels will be falsely reduced

Question 15

Give 3 uses of ATP

Answer 15

• Muscle contraction
• Active transport
• Biosynthesis
• Cell signalling

Question 16

What is the role of NAD+ and FAD as electron carriers?

Answer 16

Receive a pair of high energy electrons in chemical reactions

Question 17

What is the role of acetyl-coenzyme A in biosynthesis?

Answer 17

Used to add 2 carbon units

Question 18

What is gluconeogensis?

Answer 18

Biosynthesis of glucose in the liver (some in the kidney)

Question 19

One molecule of NADH results in how many molecules of ATP in the ETC?

Answer 19

2.5

Question 20

What are the 4 main processes in the nitrogen cycle?

Answer 20

• Nitrogen fixation
• Ammonification
• Nitrification
• Denitrification

Question 21

Where does symbiotic nitrogen fixation occur?

Answer 21

In plants that harbour nitrogen fixing bacteria (Rhizobium) within their tissues

Question 22

What is mutualism?

Answer 22

A symbiotic relationship in which both partners benefit

Question 23

What are nitrates and nitrites taken up by plants reduced to?

Answer 23

Ammonia

Question 24

What is the biological molecule that transmits signals across synapses and is the main excitatory neurotransmitter in the CNS?

Answer 24

Glutamate

Question 25

What is transamination?

Answer 25

Chemical reaction between an amino acid and a keto acid, where groups are exchanged so the amino acid becomes a keto acid and the keto acid becomes an amino acid

Question 26

Where is urea produced?

Answer 26

Liver by transamination and deamination reactions

Question 27

Where is urea excreted?

Answer 27

In the kidneys, saliva and sweat

Question 28

How is nitrogen excreted in aquatic animals?

Answer 28

Directly as ammonium as it is rapidly diluted - ammonotelic

Question 29

How do birds and non-aquatic reptiles excrete nitrogen?

Answer 29

Uricotelic - as uric acid

Question 30

Why are there no essential amino acids required by a ruminant?

Answer 30

Microbes in the rumen can synthesise all 20

Question 31

What are the functions of protein?

Answer 31

1. structural - collagen, keratin 2. movement - actin and myosin 3. immune system - antibodies 4. endocrine - hormone and receptors 5. transport - haemoglobin 6. enzymes

Question 32

Describe a protein's primary structure

Answer 32

Chains of amino acids are joined by peptide bonds between COO groups and NH3 groups

Question 33

Describe the quaternary structure of a protein

Answer 33

Interactions between different protein subunits held together by side chain interactions

Question 34

Compare globular and fibrous proteins, giving examples

Answer 34

``` Globular = folded into compact structures, soluble, e.g. enzymes, antibodies Fibrous = multiple strands held by strong bonding, insoluble, e.g. collagen, keratin ```

Question 35

What are prions?

Answer 35

Infectious proteins that cause a host's normal proteins to switch to a conformation that readily aggregates, causing cell death

Question 36

What is the main role of enzymes?

Answer 36

Increase the rate of a chemical reaction without being changed at the end - catalysts

Question 37

Where on an enzyme performs the catalytic reaction?

Answer 37

Enzymes active site

Question 38

Which weak forces are involved in binding of substrates to amino acid side chains?

Answer 38

- electrostatic attraction - hydrogen bonds - Van der Waals forces - hydrophobic interactions

Question 39

What is isosteric substrate binding?

Answer 39

Rate of reaction increases with substrate concentration until enzyme is saturated

Question 40

What is allosteric substrate binding?

Answer 40

Substrate induces a conformational change in the enzyme that increases activity - S shaped saturation curve

Question 41

What is the purpose of feedback inhibition?

Answer 41

Prevents the build up of intermediates and unnecessary use of energy

Question 42

What is a competitive inhibitor?

Answer 42

Binds to the enzymes active site

Question 43

What is a non-competitive inhibitor?

Answer 43

Bind to the enzymes allosteric site irrespective of whether a substrate is bound

Question 44

What is an uncompetitive inhibitor?

Answer 44

Bind to the enzyme substrate complex

Question 45

What 5 factors affect enzyme activity?

Answer 45

1. substrate conc 2. temperature 3. pH 4. post-translational modification 5. coenzymes and cofactors

Question 46

How does temperature affect enzyme activity?

Answer 46

Proportion of molecules with energy sufficient to overcome the activation energy increases

Question 47

How does pH affect enzyme activity?

Answer 47

All enzymes have an optimum. small deviations lead to decreased activity, can lead to denaturation of the enzyme

Question 48

What do many enzymes require to function?

Answer 48

Cofactors - small non-protein units

Question 49

What are isoenzymes?

Answer 49

Different forms of an enzyme which catalyse the same reaction

Question 50

Name the unsaturated fatty acid present in phospholipids

Answer 50

Arachidonic acid

Question 51

What are the roles of lipids?

Answer 51

- Cell membranes - Fuel - Heat insulation - Signalling molecules - Vitaminas - Nervous system

Question 52

Breifly describe lipid digestion

Answer 52

- Bile salts emulsify fat droplets - Absorbed by intestinal epithelia - Fats are reassembled and added to chylomicrons - Chylomicrons secreted to lymph and transported to the liver

Question 53

How is fat storage altered by insulin?

Answer 53

Insulin promotes fat storage

Question 54

What is hydrolysis?

Answer 54

Cleavage of chemical bonds by the addition of water

Question 55

Name the catabolic process in which fatty acid molecules are broken down in the mitochondria?

Answer 55

B-Oxidation

Question 56

What is generates from B-oxidation?

Answer 56

Acetyl-CoA

Question 57

Where do the products of B-oxidation enter?

Answer 57

The TCA cycle

Question 58

What is acetyl-CoA converted to if it doesn't enter the TCA cycle?

Answer 58

Acetone, Acetoacetate and D-3-hydroxybutyrate

Question 59

What is acetone used for?

Answer 59

It is exhaled as an emergency fuel source

Question 60

How does a high level of ketone bodies affect the blood?

Answer 60

Makes it more acidic causing metabolic acidosis as pH buffer systems become exhausted